The invention relates to a gas charging device for hydropneumatically pressurizing a vehicle suspension fluid spring or damper such as an air spring shock absorber or a MacPherson strut, and more particularly relates to a gas charging device which mechanically deflects a gas seal for introducing gas under pressure to the damping chambers of a vehicle damper.
Heretofore, shock absorbers and struts have been pressurized by drilling a hole in the outer wall of the shock cylinder. After pressurizing the cylinder through the drilled passage, the passage is sealed by pressing a plug or ball into the drilled passage. Alternatively, the passage may be sealed by welding after the passage has been closed by the plug.
This method requires several operations such as drilling and welding which, at best, impose additional expenses and the chance that metal chips or weld contaminants may be introduced in the damper assembly.
Another method of pressurizing vehicle dampers utilizes excessively high gas pressure over the piston rod seal to displace the seal and force the gas past the seal and into the chamber. Such a method makes control of the final pressure level within the damper rather difficult. The final internal pressure depends on many variables such as, the preload on the seal by the retention spring of the damper, the interface between the sealing face of the seal and the piston rod, as well as other variables.